1. Soil Physical Properties

2. Soil Physical Properties
Color
Texture
Density (particle density vs. bulk density)
Pore space (porosity)
Structure
Aggregate stability

3. Physical properties are important
1) Control plant growth through influence on:
Soil temperature (darker = warmer)
Soil aeration (sandy soils well aerated)
Soil moisture content (clayey soils stay wet)
2) Indicate important characteristics of a soil
e.g., lots vs. little organic matter

4. Objectives Know what color tells you about a soil
Describe the concept of soil texture and its importance
Use the textural triangle to determine a soil’s textural class based on its sand, silt and clay content

5. Physical properties – Color
covaries with
O.M.
Fe and Al oxides
moisture saturation
mineralogy (e.g., calcite, hematite=Fe2O3)

6. Color “quantified” using the Munsell system
Hue (e.g., 10YR) tells you general shade (red, yellow); DOES NOT tell you how dark the soil is
Value (e.g., 10YR 5/6) tells you how dark the soil is: 0 is darkest
Chroma (e.g., 10YR 5/6) tells you brightness (0 = gray). Indicates moisture conditions (bright = dry)

7. Go clockwise to numerically
Soil Color: Hue
10R
10Y
10YR
2.5 YR
5YR
7.5 YR
10R
10Y
10G
10B
10P
2.5 Y
5 Y
7.5 Y
Go clockwise to numerically
add next color!

8. Color
Chroma is used in defining wetlands.

9. 10YR page of Munsell color book
(also see Fig 4.1 of your text)

10. Example Question
Which soil horizon likely has more organic matter, one that is classified as 5R 5/6, or one that you decide is 10YR 1/7?